considerably higher than that of the plant material from which it 

 originated (Boysen-Jensen 1914). All subsequent work has shown similar 

 results (Figure 2). The process of protein enrichment has been ascribed 

 to the buildup in microbial population attendant to the detritus particles, 

 such as bacteria, fungi, diatoms, and protozoa. Specific amino acids or 

 total protein increase has been demonstrated in marsh grass, Spartina ; 

 marsh rush, Juncus ; marsh sedge, Scirpus ; eel and turtle grasses, Zostera 

 and Thalassia ; and mangrove leaves, Rhizophora spp . The high caloric 

 value, high protein content, and microbial loads of the marsh plant 

 detritus exported by tides from coastal marshes indeed represent a food 

 source of high nutritional value to estuarine consumers. 



Organic matter produced on the marsh is incorporated in estuarine 

 waters in different forms. Dead but intact shoots of marsh plants are 

 carried from the marsh by spring tides and by wind-driven tides, such 

 as the seasonal storm tides. Along the south Atlantic coast, it is not 

 uncommon to see rafts and shoals of Spartina shoots drifting out to sea 

 with the tide. Depending on the height of the prevailing tide, 2 to 16 

 kilograms of floating debris can be exported during one tidal cycle from 

 a small tidal creek draining 10 to 25 hectares (ha) of a Spartina marsh 

 watershed. Massive accumulations of fragments from dead Juncus leaves 

 are often seen piled along beaches and shores of the Gulf coast. Another 

 study has shown that roughly 3 kilograms of floating debris are exported 

 from a tidal creek draining a 6-ha marsh watershed dominated by Juncus . 

 The back-and-forth movement of the tide breaks these materials into bits 

 and pieces that are eventually washed out to sea. 



Energy is also exported from the marsh in the form of traction 

 materials that are rolled along the banks and bottoms of bayous and 

 tidal creeks as the tide ebbs. It has been shown that dissolved organic 

 substances are leached from decaying plant tissues, and that a great 

 deal of these nutrients are leached from the marsh sediment, presumably 

 from plant materials buried in the mud and from the massive mats of 

 rhizomes and roots. 



For the most part, however, past and current investigations nave 

 focused on the transport of energy from the marsh to estuarine waters 

 in the form of suspended particulate detritus. The pronounced turbidity 

 of water in bays and sounds is due primarily to the presence of detrital 

 materials that are continuously being washed out of marshes and other 

 wetlands by tides. The particulate detritus remaips suspended in the 

 water, and, in many instances, comprises the bulk of the particulate 

 organic load (i.e., seston) of the water, A review of several investi- 

 gations indicates that at least 90 percent of seston in marsh-estuaries 

 is organic detritus and that the seston constituent of marine waters is 

 generally 75 to 95 percent detritus (de la Cruz 1973). 



IX 



